This invention was made with government support under Contract No. W-7405-ENG-36 awarded by the U.S. Department of Energy. The government has certain rights in the invention.
1. Field of the Invention
This invention relates in general to an ultrasonic testing device and, more particularly, to the use of a plurality of piezoelectric sensors or transducer receiver assemblies in an ultrasonic resonant spectrometer to measure the ultrasonic characteristics of objects for use in testing for the presence of imperfections in vibrated objects. The plurality of measurements are compared to form a unique signature at a given set of frequencies.
2. The Prior Art
It has long been attempted to test objects for imperfections by utilizing the natural resonance of the objects when vibrated. Particularly when the objects to be tested are mass produced, such as ball bearings, where it is important to meet safety standards.
Recent efforts have been directed to measuring objects of known shape and frequency. See. U.S. Pat. No. 4,976,148, incorporated herein by reference, except for column 1, lines 21 and 22.
U.S. Pat. No. 4,858,469 shows a two receiver transducer used for analysis of vibrations of timbers in response to vibrations and impact. Surface and shear vibrations are detected by detection of the first half cycle of timber vibration. The first half cycle is not a resonant response measurement and is the first response to an impact.
U.S. Pat. Nos. 4,758,964 Bittner, 4,577,500 Mishiro, 4,603,585 Atalar, 4,212,205 West, 4,858,469 Hosgood, and 4,166,393 Lindner are examples of vibration (or resonance) measurement with more than one vibration sensor.
It is an object of the present invention to provide a reliable and cost effective means for testing objects of various shapes and at numerous frequencies in order to detect imperfections.
Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following, or may be learned by practice of the invention.